This invention relates to an angular positioning arrangement, and in particular to an angular positioning arrangement suitable for use in securing a rotor of a resolver or position sensor associated with a rotary shaft of an actuator against angular movement relative to that shaft. However, it may be used in other applications.
Where a resolver or rotary position sensor is associated with a rotatable shaft, for example associated with an actuator, to provide position information, it is important that the rotor of the resolver or position sensor is firmly and reliably secured to the shaft in a known angular position relative to the shaft. Any movement of the rotor relative to the shaft, or incorrect angular installation of the rotor relative to the shaft, may result in incorrect position information being supplied to an associated controller which could result in inappropriate control over the actuator or other device of which the shaft forms part or with which it is associated. Furthermore, it is desirable for the axial position of the rotor to be accurately aligned with an associated stator.
One technique used in positioning and securing a rotor of a position sensor or resolver to a shaft is to, prior to installation, move the rotor of the sensor relative to a stator thereof until the output of the position sensor reaches a null-point value. Once this position has been reached, the rotor and stator are both marked to indicate the relative positions occupied by the rotor and stator when in the null-point position. The stator is then mounted in position upon the actuator or other device with which it is to be used such that the stator position is fixed. The rotor is then positioned upon the actuator shaft, with the actuator occupying a known position which will, in use, correspond to the null-point position of the sensor. Keeping the shaft stationary, the rotor position is adjusted to bring the markings into alignment with one another.
In order to secure the rotor in this position relative to the shaft, the rotor is formed with a pair of slots. Once correctly positioned upon the shaft, the shaft is deformed, for example by swaging, to force part of the shaft material into the slots of the rotor, and thereby prevent relative movement between the shaft and the rotor.
US2011/0241498 describes another technique for securing a resolver rotor to a shaft. It includes a bearing by which the resolver is mounted upon the shaft, and a lock arrangement for locking the resolver in a chosen angular orientation relative to the shaft.
US2008/0279652 describes a coupling in which one component is provided with a series of serrations received within recesses formed in another component.
There is a desire to provide an alternative positioning arrangement whereby a rotor can be secured to a shaft in a desired angular position. Furthermore, there is a desire to provide an arrangement which allows removal of the rotor from the shaft, for example to allow replacement of the rotor in the event that replacement thereof is required.